For effective fire prevention and fire fighting, additives with thickening properties are used to increase the viscosity of the firefighting water, in order to achieve, in comparison to water, an improved adhesion of the fire-extinguishing agent to surfaces, in particular to sloped surfaces. The majority of the known firefighting water additives include water-swellable polymers, which nevertheless are restricted in their applicability because of their solid, granular structure.
In order to overcome this disadvantage, polymer dispersions in the form of water-in-oil emulsions have been used recently, as described in EP 0 774 279 B1. These emulsions include a continuous oil phase, in which particles of a cross-linked, water-swellable polymer are dispersed. The polymer particles have particle sizes of less than 2 μm, whereby extremely short swelling times of less than 3 seconds result. Along with their high water absorption capacity the water-in-oil emulsions have the properties of a thickening agent so that after their mixing with water a highly viscous fire-extinguishing agent or fire-preventing agent is obtained which adheres well to any type of surface, in particular to sloped surfaces.
Disadvantageous in all the additives to firefighting water is their comparatively low environmental compatibility, in particular their toxic action with respect to microorganisms such as algae and daphnia. As a measure for the toxicity of a substance with respect to algae, EC50 values are used which are determined according to the OECD Guideline 201, and, as a measure for the toxicity of a substance with respect to daphnia, corresponding EC50 values are used which are determined according to the OECD Guideline 202, Part 1. Due to their toxicity with respect to algae or daphnia, the known firefighting water additives are classified according to European law as “environmentally hazardous” and must be designated with the hazard symbol “N”. The use of firefighting water additives according to the state of the art is thus, from ecological points of view, above all questionable when they are to be used in the wild, therefore away from places which are equipped with a water system or water retention basins, such as, for example, in forest fires or bush fires.
An objective of the present invention is thus to provide environmentally compatible polymer dispersions which can be used as additives to firefighting water.